In vertical roller mills, material distribution on the grinding table depends on many factors (grinding stock, rotational speed, grinding bed height, feed point, etc.) which sometimes even influence one another.
DD 106 953 A1 and DE 44 43 099 A1 disclose methods for the comminution of grinding stock in a vertical roller mill, the grinding stock being fed to at least one grinding roller in order to form a grinding bed and being comminuted between a grinding table and the at least one grinding roller. On account of the geometry of the grinding roller, a grinding bed of differing height is formed over the width of the grinding roller.
DD 225 634 A1 discloses a roller mill with a feed device, by means of which a grinding bed formed as uniformly as possible can be achieved.
DE 196 51 103 A1 addresses the problem of air included in the grinding bed and, in order to deaerate the grinding stock located on the grinding table, proposes to feed the grinding stock to the grinding table in layers, the fine stock fraction forming essentially a lower first grinding stock layer and the coarse stock fraction forming essentially a second grinding stock layer, lying above it, in the grinding bed. According to a first variant, the grinding stock is fed centrally, whereas, in a second exemplary embodiment, separate feeding upstream of each grinding roller takes place.
To improve the grinding stock drawing-in conditions of the grinding roller and to ensure more efficient grinding, DE 197 23 100 A1 proposes stock guide elements or stock guide blades which are held on common carrying arms arranged above the grinding table and in this case can be set in respect of their elevation and/or in respect of a stock guide direction.
Nevertheless, in spite of these known measures, during grinding operation vibrations repeatedly occur and are then kept low by means of a high grinding bed or an injection of water at the expense of grinding efficiency.